Butyl ester ions, decomposition

The esters differ from each other in stability. To decompose the isopropyl ester, higher temperatures and higher acid strengths are needed than for decomposition of the s-butyl ester. It is claimed that the resulting carbenium ions are stabilized by solvation through the acid (25-27). Branched alkenes do not form esters. It is believed that they are easily protonated and polymerized (28). 

The r-butyl reactant ions are formed in the near vicinity of the electron beam, and they drift to the ion exit slit of the ionization chamber under the influence of the repeller field. Protonated ester molecules (taken as a typical example) are formed along the path of the r-butyl ions by proton-transfer reactions, and after formation the protonated ester ions drift toward the ion exit slit under the influence of the repeller field. In the process of doing this they undergo decomposition reactions which may be looked upon as a set of parallel, competing first-order reactions, that is. 

The para-nitro ester 71d generated only 4-nitroaniline (70%) and 4,4 -dinitroazoxybenzene (10%) when it underwent decomposition (Scheme 29). These products could have been derived from either a triplet nitrene or a triplet nitrenium ion precursor. Homolysis of the N—O bond to generate radical intermediates was ruled out because of the nearly quantitative yield of pivalic acid derived from 71d. The pivaloxy radical would have undergone rapid decarboxylation to generate CO2 and the rert-butyl radical under these conditions. Since no rearrangement product was observed, it was tentatively concluded that this ester underwent direct decomposition to 4-nitrophenyl-nitrene without the intermediacy of a nitrenium ion. ... 

A consequence of the addition of coordinated OH- to alkenes is that other nucleophilies, for example a coordinated aminate ion, should also be active. This type of reaction is seen with the chloropentaammine complex [Co(NH3)500CCH=CHC02Bu,]2+ in aqueous base533 (Scheme 49). The reaction of the f-butyl maleate complex occurs to the extent of ca. 50% and is complicated by hydrolysis of the maleate ester and some decomposition of the cobalt(III) complexes. Reactions of this type have recently been exploited in the synthesis of j3-carboxyaspartic acid in the coordination sphere of cobalt(III).53... 

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